This application is based on Application No. 2000-211521 filed in Japan, the content of which is hereby incorporated by reference.
The present invention relates to a communication device, and more particularly to a communication device having an image transmission function such as a videophone or a camera-equipped cellular phone.
Communication devices having an image transmission function, such as videophones and camera-equipped cellular phones, are widely commercialized. Using such a device, not only the voice but also the facial expressions of the speaker may be mutually exchanged and recognized during communication between remote locations.
However, because the focal length of the optical system included in the camera is fixed in a conventional device, when the captured image is displayed in the display unit, the object is not often displayed in the optimal size. For example, while it is desirable for a videophone or camera-equipped cellular phone to capture the image of the person who is a party to the conversation such that his or her face is displayed essentially in the center of the screen at all times, because the focal length of a conventional device is fixed, it is difficult to use the optimal size for the object image included in the displayed image.
The present invention provides a communication device having an image transmission function that is capable of capturing an object image using the optimal size.
In one embodiment of the invention, there is a communication device having an image transmission function, the device including a lens unit with a variable focal length used for capturing images; a magnification setting unit that sets the magnification used during image capture by the lens unit to a prescribed value when power is turned ON; and a lens driving unit that determines an initial focal length based on the image capture magnification set by said magnification setting unit and changes the construction of said lens unit based on said initial focal length.
In one aspect of the invention, the lens unit includes an aperture with an adjustable opening diameter, and the lens driving unit adjusts the opening diameter of said aperture based on the image capture magnification set by the magnification setting unit.
In another aspect of the invention, the magnification setting unit sets the image capture magnification, which is expressed as xcex21, to a value within the range 0.003 less than |xcex21| less than 0.08. |xcex21| is an absolute number of xcex21.
In yet another aspect of the invention, the device further includes switching unit that alternates the mode between a one-person image capture mode and a two-person image capture mode, and the magnification setting unit sets the image capture magnification to a smaller value when the two-person mode is selected than when the one-person image capture mode is selected.
In still another aspect of the invention, the device includes operation input unit that sets and inputs a focal length for the lens unit, and focal length changing unit that changes the initial focal length based on the focal length set and input by the operation input unit.
In another aspect of the invention, the focal length changing unit changes the initial focal length when an instruction is input from the operation input unit to change the initial focal length.
In still another aspect of the invention, the focal length changing unit changes the initial focal length each time a focal length is set and input from the operation input unit.
In another embodiment of the invention, the device includes a lens unit having a variable focal length used for capturing the image of the object; distance measuring unit that measures the distance from the object and generates distance information; and a lens driving unit that determines the optimal focal length for capturing the image of the object using a prescribed image capture magnification based on the distance information and drives the lens unit to match the optimal focal length.
In one aspect of the invention, the lens driving unit determines the optimal focal length and drives the lens unit each time the distance information changes.
In still another aspect of the invention, the device includes a lens unit having a variable focal length used for capturing the image of the object; an image processing unit that performs image processing of the image obtained through image capture of the object and determines the magnification adjustment amount required for image capture of the object using a prescribed image capture magnification; and a lens driving unit that drives the lens unit based on the magnification adjustment amount.
In yet another aspect of the invention, the image processing unit determines the magnification adjustment amount each time the image obtained through image capture of the object changes, and the lens driving unit drives the lens unit each time the magnification adjustment amount is sought.